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CHAPTER 2

Object-Oriented and Classical Software Engineering Fifth Edition, WCB/McGraw-Hill, 2002 Stephen R. Schach srs@vuse.vanderbilt.edu. CHAPTER 2. THE SOFTWARE PROCESS. Overview. Client, Developer, and User Requirements Phase Specification Phase Design Phase Implementation Phase

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CHAPTER 2

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  1. Object-Oriented and Classical Software EngineeringFifth Edition, WCB/McGraw-Hill, 2002Stephen R. Schachsrs@vuse.vanderbilt.edu

  2. CHAPTER 2 THE SOFTWARE PROCESS

  3. Overview • Client, Developer, and User • Requirements Phase • Specification Phase • Design Phase • Implementation Phase • Integration Phase • Maintenance Phase • Retirement • Problems with Software Production: Essence and Accidents • Improving the Software Process

  4. The Software Process • The life-cycle model • CASE tools • The individuals

  5. Terminology • Systems analysis • Requirements + specifications phases • Operations mode • Maintenance • Design • Architectural design, detailed design • Client, developer, user • Internal software development/contract software

  6. Testing Phase? • There is NO testing phase • Testing is an activity performed throughout software production • Verification • Performed at the end of each phase • Validation • Performed before delivering the product to the client

  7. Documentation Phase? • There is NO documentation phase • Every phase must be fully documented before starting the next phase • Postponed documentation may never be completed • The responsible individual may leave • The product is constantly changing—we need the documentation to do this • The design (for example) will be modified during development, but the original designers may not be available to document it

  8. Requirements Phase • Assumption • The software being considered is economically justifiable • Concept exploration • Determine what the client needs, not what the client wants • Moving target problem

  9. Requirements Phase Testing • Rapid prototyping

  10. Requirements Phase Documentation • Rapid prototype, or • Requirements document

  11. Specification Phase • Specifications document (“specifications”) • Legal document • Must not have phrases like “optimal,” or “98% complete”

  12. Specification Phase (contd) • Specifications must not be • Ambiguous • Incomplete • Contradictory

  13. Specification Phase (contd) • Once the specifications have been signed off • The software product management plan (SPMP) is drawn up • This is the earliest possible time for the SPMP

  14. Specification Phase Testing • Traceability • Review • Check the SPMP

  15. Specification Phase Documentation • Specification document (specifications) • SPMP

  16. Design Phase • Specification—what • Design—how • Retain design decisions • When a dead-end is reached • For the maintenance team • Ideally, the design should be open-ended • Architectural design • Decompose the product into modules • Detailed design • Design each module: data structures, algorithms

  17. Design Phase Testing • Traceability • Review

  18. Design Phase Documentation • Design • Architectural design • Detailed design

  19. Implementation Phase • Implement the detailed design in code

  20. Implementation Phase Testing • Review • Test cases • Informal testing (desk checking) • Formal testing (SQA)

  21. Implementation Phase Documentation • Source code • Test cases (with expected output)

  22. Integration Phase • Combine the modules and check the product as a whole

  23. Integration Phase Testing • Product testing • Acceptance testing

  24. Integration Phase Documentation • Commented source code • Test cases for the product as a whole

  25. COTS Software • “Shrink-wrapped software” • Commercial off-the-shelf (COTS) • Nowadays, COTS software is often downloaded • “Click-wrapped software” • Alpha testing • Beta testing

  26. Maintenance Phase • Maintenance • Any change once the client has accepted the software • The most money is devoted to this phase • The problem of lack of documentation

  27. Maintenance Phase Testing • Regression testing

  28. Maintenance Phase Documentation • Record of all changes made, with reasons • Regression test cases

  29. Retirement • Good software is maintained • Sometimes software is rewritten from scratch • Software is now unmaintainable because • A drastic change in design has occurred • The product must be implemented on a totally new hardware/operating system • Documentation is missing or inaccurate • Hardware is to be changed—it may be cheaper to rewrite the software from scratch than to modify it • True retirement is a rare event

  30. Process-Specific Difficulties • Does the product meets the user’s real needs? • Is the specification document free of ambiguities, contradictions, and omissions?

  31. Inherent Problems of Software Production • Hardware has inherent limits • So does software • No Silver Bullet • Complexity • Conformity • Changeability • Invisibility • Aristotelian categories • Essence • Accidents

  32. Complexity • Software is far more complex than hardware • Traditional abstraction will not work • We cannot understand the whole, so we cannot understand any part • Management is difficult • Maintenance is a nightmare (documentation, too)

  33. Conformity • Type 1: Existing gold refinery • Type 2: New gold refinery

  34. Changeability • Software is easier to change than hardware • Pressure to change • Reality • Useful software • Easier to change • Software has a long lifetime (~15 yrs) compared to hardware (~4 yrs)

  35. Invisibility • Software is invisible and unvisualizable • Complete views are incomprehensible • Partial views are misleading • However, all views can be helpful

  36. Is There a Silver Bullet? • What about • High-level languages • Time sharing • CASE tools • These did not solve the intrinsic problems • We have experienced • 6% annual productivity increase • But, no “silver bullet” (order-of-magnitude increase) is possible

  37. Improving the Software Process • U.S. Department of Defense initiative • Software Engineering Institute (SEI) • The fundamental problem with software • The software process is badly managed

  38. Improving the Software Process (contd) • Software process improvement initiatives • Capability maturity model (CMM) • ISO 9000-series • ISO/IEC 15504

  39. Capability Maturity Model • Not a life-cycle model • Set of strategies for improving the software process • SW–CMM for software • P–CMM for human resources (“people”) • SE–CMM for systems engineering • IPD–CMM for integrated product development • SA–for software acquisition • These strategies are being unified into CMMI (capability maturity model integration)

  40. SW–CMM • A strategy for improving the software process • Put forward in 1986 by the SEI • Fundamental idea: • Improving the software process leads to • Improved software quality • Delivery on time, within budget • Improved management leads to • Improved techniques • Five levels of “maturity” are defined • Organization advances stepwise from level to level

  41. Level 1. Initial Level • Ad hoc approach • Entire process is unpredictable • Management consists of responses to crises • Most organizations world-wide are at level 1

  42. Level 2. Repeatable Level • Basic software management • Management decisions should be made on the basis of previous experience with similar products • Measurements (“metrics”) are made • These can be used for making cost and duration predictions in the next project • Problems are identified, immediate corrective action is taken

  43. Level 3. Defined Level • The software process is fully documented • Managerial and technical aspects are clearly defined • Continual efforts are made to improve quality, productivity • Reviews are performed to improve software quality • CASE tools are applicable now (and not at levels 1 or 2)

  44. Level 4. Managed Level • Quality and productivity goals are set for each project • Quality, productivity are continually monitored • Statistical quality controls are in place

  45. Level 5. Optimizing Level • Continuous process improvement • Statistical quality and process controls • Feedback of knowledge from each project to the next

  46. Summary

  47. Key Process Areas • There are key process areas (KPAs) for each level • Level 2 KPAs include: • Requirements management • Project planning • Project tracking • Configuration management • Quality assurance • Compare • Level 2: Detection and correction of faults • Level 5: Prevention of faults

  48. Experience • It takes: • 3 to 5 years to get from level 1 to level 2 • 1.5 to 3 years from level 2 to level 3 • SEI questionnaires highlight shortcomings, suggest ways to improve the process • Original idea: Defense contracts would be awarded only to capable firms

  49. Experience (contd) • Profitability • Hughes Aircraft (Fullerton, CA) spent $500K (1987–90) • Savings: $2M per year, moving from level 2 to level 3 • Raytheon moved from level 1 in 1988 to level 3 in 1993 • Productivity doubled • Return of $7.70 per dollar invested in process improvement

  50. Other SPI Initiatives • Other software process improvement (SPI) initiatives: • ISO 9000-series • ISO/IEC 15504

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